Many industries, including the assembly processing, grocery and food processing industries, transportation, and multimedia industries, utilize an identification system in which the products are marked with an optical code (such as a bar code symbol consisting of a series of lines and spaces of varying widths, or other type of symbols consisting of series of contrasting markings, generally known as two dimensional symbology). A number of different optical code readers and laser scanning systems have been developed to decode the optical pattern to a multiple digit representation for inventory, production tracking, check out or sales. Some of optical reading devices are also used to take pictures and display, store or transmit real time images to another system.
Optical readers or scanners are available in a variety of configurations, some of which are built into a fixed scanning station and others of which are portable. The portability of an optical reading device provides a number of advantages, including the ability to inventory products on shelves and to track portable items such as files or small equipment. A number of these portable reading devices incorporate laser diodes which permit the user to scan the symbology at variable distances from the surface on which the optical code is imprinted. A disadvantage of known laser scanners is that they are expensive to manufacture and do not provide the ability to reproduce the image of the targeted area by the sensor and therefore limits the field of use of optical code reading devices. Additionally laser scanners typically require a raster scanning technique to read and decode a two dimensional optical code.
Another type of optical code reading device, generally known as scanner or imager, which can be incorporated into a portable system uses light emitting diodes (LEDs) as a light source and charge coupled devices (CCD) or Complementary metal oxide silicon (CMOS) sensors as detectors. This class of scanners or imagers is generally known as "CCD scanners" or "CCD imagers". CCD scanners take a picture of the optical code and stores the image in a frame memory, which is then scanned electronically, or processed using software to convert the captured image into an output signal.
One type of such CCD scanner is disclosed in earlier patents of the present inventor, Alexander Roustaei. These patents include U.S. Pat. Nos. 5,291,009, 5,349,172, 5,354,977, 5,532,467, and 5,627,358. While CCD scanners have the advantage of being less expensive to manufacture, the scanners prior to Roustaei were limited to scanning the optical code by either contacting the surface on which the optical code is imprinted or maintaining a distance of no more than one and one-half inches away from the optical code, which creates a further limitation in that it cannot read optical code any bigger than the window or housing width of the reading device. The CCD scanner disclosed in U.S. Pat. No. 5,291,009 and its offspring introduced the ability to read symbologies which are wider than the physical width and height of the scanner housing at distances as much as twenty inches from the scanner or imager. This added versatility to CCD scanners which previously were limited to contact and close range, now allowing the CCD scan engines or imagers to be incorporated in fixed scanner systems, such as are used at retail checkout counters.
Considerable attention has been directed toward the scanning of two-dimensional symbologies, which can store about 100 times more information in the same space occupied by a one-dimensional symbology. In two-dimensional symbologies, rows of lines and spaces are either stacked upon each other or they form matrix of black and white square, rectangular or hexagon cells. The symbologies or the optical codes are read by scanning a laser across each row, in the case of stacked symbology, in succession in a zig-zag pattern. A disadvantage of this technique is that it introduces the risk of loss of vertical synchrony due to the time required to scan the entire optical code. It also has the disadvantage of requiring a laser for illumination and moving part for generating the zig-zag pattern, in order to scan the entire symbology, which makes the scanner more expensive and less reliable due to mechanical parts.
In all types of optical codes, i.e., one-dimensional, two-dimensional and even three- dimensional (multi-color superimposed symbologies), the performance of the optical system needs to be optimized to provide the best possible resolution, signal-to-noise ratio, contrast and response. These and other parameters are controllable by selection of, and adjustments to, the optical components, e.g., lens system, the wavelength of illuminating light, the optical and electronic filtering, and the detector sensitivity.
A further disadvantage of scanning two-dimensional symbologies is that it takes an increased amount of time and image processing power to capture the image and process it, i.e., increased microcomputer memory and faster duty-cycle processor.
Another disadvantage of known apparatus for scanning symbologies is that the high-speed processing chips they require are costly, generate heat and occupy space.
Accordingly, there is a need for, and it is an object of the invention to provide a system for scanning symbologies that integrates the necessary components onto a single chip or a reduced number of chips. It is also an object of the present invention to reduce the amount of on-board memory and to provide a system requiring a reduced amount of power and having a lower level of heat generation.
A further object of the invention is to provide a scanning or imaging device employing a high quality and high speed image processing system, including image grabbing, image processing and decoding functions, of the target symbology or optical code.
Another object of the invention is to provide scanners or imagers having variable depth of field with means for aiding an operator in framing symbology, i.e., targeted area, so that is captured in the appropriate field of view.
A further object of the invention is to provide an imaging device able to scan a plurality of symbologies within one optically scanned image field, and then separate or segment the image field into individual symbology fields at high speed.